1. Field of the Invention
The present invention relates to an insulating film forming method and an insulating film forming apparatus each for forming an insulating film composed of two or more layers on a substrate such as a semiconductor wafer or the like.
2. Description of the Related Art
A technique for flattening a layer insulating film formed on a semiconductor wafer (hereinafter referred to only as xe2x80x9ca waferxe2x80x9d) is especially important in multilayer interconnection techniques. As one example of the technique, a technique for making the layer insulating film multilayered is given.
For example, in Japanese Patent Laid-open No. Hei 10-135201, a method for forming such a layer insulating film is disclosed. According to this method, an inorganic SOG solution is applied on a foundation layer insulating film by spin coating, and pre-drying is performed by heating to a temperature between about 100xc2x0 C. and about 250xc2x0 C. to form an inorganic SOG film (a first insulating film). On the inorganic SOG film, a silicon oxide film (a second insulating film) is formed by a plasma CVD method with TEOS as a base.
There is, however, a problem that low dielectric constant properties of the first insulating film and the second insulating film are deteriorated by chemical reaction if the second insulating film is formed by the CVD method as described above.
Further, according to experiments by the present inventor, et al., it is proved that the adhesion of the first insulating film and the second insulating film is poor if the second insulating film is formed by the CVD method.
Furthermore, in the aforesaid method, the first insulating film is formed by the spin coating accompanied by single wafer processing, whereas the second insulating film is formed by the CVD method accompanied by batch processing, whereby the structure of separate apparatus (for example, structure in which the wafer is transferred between these apparatus by using an AGV) is needed, causing a problem in terms of production efficiency and apparatus costs.
Moreover, in the aforesaid method, only pre-drying is performed by heating to the temperature between about 100xc2x0 C. and about 250xc2x0 C. after the application of the inorganic SOG solution, and hence the first insulating film also needs to be burned after the formation of the second insulating film, which causes a problem that it is required to select a permeable material as the second insulating film.
An object of the present invention is to provide an insulating film forming method and an insulating film forming apparatus capable of offering favorable low dielectric constant properties and good adhesion of a first insulating film and a second insulating film.
Another object of the present invention is to provide an insulating film forming method and an insulating film forming apparatus capable of forming the first insulating film and the second insulating film in the same apparatus.
Still another object of the present invention is to provide an insulating film forming method and an insulating film forming apparatus capable of widening the extent of selection of a material for the second insulating film.
To solve the aforesaid problems, an insulating film forming method of the present invention comprises the steps of: (a) applying a first inorganic insulating film material on a substrate; and (b) applying a second organic insulating film material on the applied first insulating film material, and further comprises thermal processing steps each with a plurality of stages at different temperatures between the step (a) and the step (b), and after the step (b) respectively.
According to the present invention, both the first insulating film and the second insulating film are formed through the step of xe2x80x9capplication of a materialxe2x80x9d without passing through the step of CVD, whereby low dielectric constant properties are favorable, the adhesion of the first insulating film and the second insulating film is satisfactory, and the first insulating film and the second insulating film can be formed in the same apparatus. Moreover, since thermal processing steps each with a plurality of stages at different temperatures, for example, drying, condensation polymerization, and burning are performed respectively after the application of the first insulating film material and after the application of the second insulating film material, it is unnecessary to burn the first insulating film after the formation of the second insulating film. Hence, it is not necessarily required to select a permeable material as the second insulating film, and consequently the extent of selection of a material for the second insulating film can be widened.
According to an aspect of the present invention, the aforesaid thermal processing steps with a plurality of stages are characterized by being set at a temperature not more than 500xc2x0 C., whereby disconnection of a wiring pattern formed at a layer lower than the insulating film, and the like can be prevented.
According to an aspect of the present invention, the thermal processing step with a plurality of stages is characterized in that the temperature is raised stepwise. Consequently, for example, drying, condensation polymerization, burning, and the like can be performed efficiently by being allocated to separate heat processing devices.
Therefore, according to an aspect of the present invention, the thermal processing step with a plurality of stages is characterized by comprising at least a thermal processing step for drying a solvent in each of the applied first and second insulating film materials, and a thermal processing step for performing condensation polymerization for the first and second insulating film materials in each of which the solvent is dried.
According to an aspect of the present invention, in order that the thermal processing step at the final stage between the step (a) and the step (b) and the thermal processing step at the final stage after the step (b) are almost the same at least with respect to temperature conditions, processing conditions in the thermal processing step before the final stage between the step (a) and the step (b) and in the thermal processing step before the final stage after the step (b) are set respectively. As a result, the thermal processing step at the final stage between the step (a) and the step (b) and the thermal processing step at the final stage after the step (b) can be performed in the same heat processing device. Especially when the thermal processing step at the final stage is a burning step, the thermal processing temperature is the highest. Thus, it is desirable in terms of the structure of the apparatus and energy to perform the thermal processing step at the final stage between the step (a) and the step (b) and the thermal processing step at the final stage after the step (b) in the same heat processing device.
According to an aspect of the present invention, the first insulating film and the second insulating film are respectively applied on the substrate by a spin coating method in the step (a) and the step (b).
An insulating film forming method of the present invention is characterized by comprising the steps of: (a) applying a first porous insulating film material on a substrate; and (b) applying a second insulating film material such that the second insulating film material is filled in holes made in the surface of the applied first insulating film material and such that the surface after application is flattened, on the applied first insulating film material.
According to the present invention, low dielectric constant properties are satisfactory, the adhesion of the first insulating film and the second insulating film is favorable, the formation of the first insulating film and the second insulating film can be performed in the same apparatus, and in addition, a flatter insulating film can be formed.
An insulating film forming apparatus of the present invention is characterized by integrally comprising: a first coating device for applying a first inorganic insulating film material on a substrate; a second coating device for applying a second organic insulating film material on the applied first insulating film material; a plurality of kinds of thermal processing devices set on different thermal processing conditions respectively, for performing thermal processing for the substrate on which the insulating film materials are applied by the first and second coating devices; and a transfer device for transferring the substrate between these devices.
According to the present invention, low dielectric constant properties are satisfactory, the adhesion of the first insulating film and the second insulating film is favorable, and moreover the first insulating film and the second insulating film can be formed in the same apparatus.
According to an aspect of the present invention, at least one thermal processing device out of the plurality of kinds of thermal processing devices is used in common by both the substrate on which the first insulating film material is applied by the first coating device and the substrate on which the second insulating film material is applied by the second coating device, which is desirable in terms of the structure of the apparatus and energy.
Therefore, according to an aspect of the present invention, the aforesaid thermal processing device for common use is characterized by being set at the highest temperature out of the plurality of kinds of thermal processing devices.
Furthermore, according to an aspect of the present invention, the first and second coating devices respectively apply a first insulating film and a second insulating film on the substrate by a spin coating method.